Treatment of elongated flexible materials such as fabrics



March 19, 1957 Filed May ll, 1955 5 Smeets-Sheet l 3" SSIWY March 19, 1957 F. G. AuDAs ETAL 2,785,478

TREATMENT 0E ELONGATED FLEXIBLE MATERIALS sucE As FABRICS f Fild May l1, 1955 5 Sheets-Sheet 2 ma@ S. STAM March 19, 1957 Filed May ll, 1955 F. G. AUDAs `ET AL 2,785,478

TREATMENT OF' ELONGATED FLEXIBLE MATERIALS SUCH AS FABRICS 5 Sheets-Sheet 3 March 19, 1957 F. G. AUDAS ETAL 2,785,478

TREATMENT OF' ELONGATED FLEXIBLE MATERIALS SUCH AS FABRICS Filed May 1l, 1955 5 Sneets-Sheet 4 March 19, 1957 F. G. AUDAS ETAL 2,785,478

TREATMENT @E EEONGATED FLEXIBLE MATERIALS SUCH As FABRICS 5 Smeets-Sheet 5 Filed May ll. 1955 S u au@ was +En .5 E@ v w n n \n GE J h L EN a a Y F wat nited States nPatent O TREATMENT F ELNGATED FLEXIBLE MATERIALS SUGH AS FABRECS Francis George Audas, Cheadle Hahne, and John Wilson, Bramhall, England, assignors to 'Ehe British Rayon Research Association, Manchester, lingiand, a Ernia-.- association Application May l1, 1955, Serial No. 567,705

Claims priority, application Great Britain May 28, 1954 22 Claims. (Cl. 34m-9) This invention relates to treatments such as the drying of elongated iiexible materials such as textile fabrics in sheet form, and has for its objects to provide a more efficient method requiring less floor space for the continuous drying of fabrics, especially textile fabrics, by the use of an improved heat transfer medium.

The need for the continuous drying of fabrics arises in a wide range of manufacturing processes. ln the manufacture and finishing for example of textile fabrics it is well known to dry the fabric after scouring, bleaching, dyeing, mercerising, moth-proofing and after treatment for crease-resistance. In the manufacture and processing of various other fibrous materials such as paper it is likewise necessary to dry at various stages. Drying is also a `feature of processes for the manufacture of sheets from various polymeric compounds.

Various methods have been used or proposed for such drying, including treatment with hot cylinders, hot air or superheated steam and infra-red rays but in these cases the apparatus required usually suffers from one or more of the faults of inefficiency, high cost of equipment, the use of an expensive form of heating, and particularly in the case of hot air heating a very large plant to utilise the high rates of air that are required because of the low heat capacity of such a gas.

According to the present invention, fabric is dried by passing the wet fabric disposed in a substantially vertical plane through a bed of hot solid discrete particles, while subjecting the bed to an upward gaseous current, the size and weight of the particles and the velocity and nature of the current being so chosen that the force exerted by the current is sutiicient to counter-balance the gravitational force on free particles and to expand the bed thus allowing movement of the particles but is insuihcient to convert the bed into a stream of particles. A bed of solid discrete particles subjected to and expanded by such an upward gaseous current in the manner described is hereinafter and in the claiming clauses hereof called a hot fluidised bed of small discrete solid particles.

The art of iluidising beds of solid discrete particies by means of a sufciently rapid upward stream of gas is well known in the chemical manufacturing industry, partie ularly in connection with the cracking of hydrocarbons but such fluidised beds have hitherto been used for the wholly different purpose of bringing finely divided catalytic materials into intimate contact at high temperatures with a moving stream of hydrocarbon vapour. The duidising of a bed of small solid discrete particles has also been applied in the liour milling industry but for the wholly different purpose of making the suspended particles of Hour more easily transportable. The use of a fluidised bed of small hot solid discrete particles in the dryingof wet fabrics has important advantages compared with the known methods of drying by means of hot air or superheated steam. rhe thermal capacity of a given volume of such a fluidised bed may be made much higher than the same volume of air or superheated steam by the use of an appropriate solid material. The solid particles of the fluidised bed possessing a very large total surface area act as an excellent heat interchanging system with the air used for liuidising and as `the particles are also free to move and collide with the fabric surface, thus con-` veying heat and also disturbing the gas layer immediately adjacent to the fabric, the fabric :surface is `always in cornl tact with a mixture of hot gases and hot particles and this results in extremely high rates of heat transfer.` Heat is transferred from a heat source within the bed by a similar process. in consequence of these characteristics of the fluidised bed method of drying it is possible to dry fabrics very rapidly with a remarkable uniformity of decree of drying in apparatus occupying smaller floor space than that required for the hot air or super-heated steam methods of drying.

We have found a finely divided silicious material, such as sand, is a convenient solid phase and air is a convenient gaseous phase of a tluidised bed for drying textile fabrics, wetted with water or other inert liquids but the nature of the solid and gaseous phases `of the fluidised bed may be varied in any individual case to suit the nature of the fabric to be dried and the characteristics of the wetting liquid.

For example in some cases when drying dyed or processed fabrics it may be convenient 'to use a gas in the gaseous phase of the fluidised bed which, in addition to serving the purpose of counter-balancing the gravitational attraction on the particles of the solid phase, also assists chemically in the dyeing or processing of the fabric. Likewise in drying fabrics such as textile fabrics for subsequent use in the manufacture of dielectrics in electrical apparatus it may be necessary to avoid particles in the solid phase of the fluidised bed of which traces in the finished fabric may adversely affect the dielectric properties of the finished fabric. it may be advantageous in the case of fabrics consisting of or containing fibrous material, such as paper, to use particles in the solid phase which when carried out of the iluidised bed as a fine layer on the surface of the dried fabric may assist in a further step in the processing or finishing of the fabric.

When using silica sand as the solid phase of the iiuidised bed for drying textile fabrics we prefer to use a particle size of not less than microns and not more than 200 microns overall diameter. We: find that with particles of less than 100 microns size there is an increased tendency for particles to be carried out of the bed, firstly, by the vapour resulting from the evaporation of the liquid on or in the fabric and, secondly, by the fabric itself, while with particles of more than 209 microns size the amount of air required. to expand the bed into the iuidised state is increased.

The gas velocity necessary for fluidising the bed is relatively low compared with the velocities used in hot air drying plants and for air is of the order of 0.5 to 2.0 ft./sec. The density of the iuidised sand corresponds very nearly to that of water and the pressure of air required for iiuidising is therefore approximately equivalent to a water gauge pressure equal to the bed depth. The upward gaseous current may be applied to the particles of the solid phase of the uidised bed by any convenient means but we prefer to use a porous ceramic partition which serves to provide a uniformly distributed resistance in the gas path and, in consequence, a substantiall;I homogeneous liuidisation of the particles of the solid phase of the fluidised bed. The space occupied by the fluidised bed may be subdivided by means of wire grids or the like for the purpose of reducing or eliminating turbulence.

The escaping gases include the vaporised liquid from the fabric and this, in the case of steam, may usefully be used for preheating a textile fabric.

The fabric to be dried may be disposed in a substantially vertical plane by lbeing led down through the fluidised bed in a substantially vertical direction or by being led through the bed in a direction at an angle to the vert-ical with the plane of the fabric substantially vertical. The fabric may be led into and out of the bed throu-gh fluidtight seals or such seals may be dispensed with by leading the fabric vertically downward into the bed and vertically upward out of the bed, guide means such as a roller being provided for changing the direction of the fabric in the bed. The roller is preferably made of porous ceramic material and is provided with an internal sir supply to assist in maintaining a uidised condition in the space between the ascending and descending sheets of fabric. The means of leading the fabric into or through the bed may include supporting belts, gauges, or felts. The fluidised bed may be combined with stentering means.

The fluidised bed may be hea-ted by any convenient means but we prefer to locate the heating means in the iluidised bed and for this purpose gas fired or steam heated pipes or electrical resistance heaters, for example, may be used.

For drying fabrics there is a relationship between the temperature of the iluidised bed and the drying time necessary; the higher the temperature the lower is the drying time required. It has been found that when drying certain textile fabric-s wetted with water a iluidised bed temperature of between 100 C. and 170 C. has been found suitable. Drying times of as little as 7 seconds may be achieved with textile fabrics wetted with water and temperatures in the upper part of the said range.

Our invention also includes apparatus for the drying of fabric, which includes Va container adapted to contain a bed of solid discrete particles when in the unfluidised and when in the hot fluidised state, the -overall particle diameter being preferably not less than 100 microns and preferably not more than 200 microns, means Ifor applying an upward gaseous current to the said bed at a pressure and velocity sufficient to counter-balance the gravitational force on free particles and to expand the bed thus allowing movement of the particles but insuflicient to convert the bed into a stream of particles, means for heating the tluidised bed and means for conveying fabric disposed in a substantially vertical plane continuously through the said fluidised bed.

The invention will now be described by way of example applied vto the drying of a textile fabric with reference to the following diagrams in which:

Fig. l is a side elevation of an apparatus or machine by means of which a method according to the invention may be put into practice and showing, in particular, the drive arrangement, and the other main parts in out-line;

Fig. 2 is a side elevation, showing the various parts in greater detail, and being partly in section to show more clearly the path taken by the fabric to be dried;

Fig. 3 is an end elevation from the right of Fig. 2 with the end of the tluidised bed compartment broken away to show the internal arrangement more clearly;

Fig. 4 is .a plan View corresponding to Fig. 2 with certain covers removed, and

Fig. 5 is a perspective View of the machine as seen in the direction of the arrow in Fig. 4.

The apparatus or machine consists essentially of a supporting structure on which is mounted a container through which the material to be dried is progressed. The lower part of the container (hereinafter referred to in this description as the bed compartment) is adapted to hold a bed formed by a mass of particles, and auxiliary apparatus provided whereby this bed may be uidised land heated. Positively driven means are also provided for progressing the material through the container.

The supporting structure comprises four vertical channel irons l0, one at each corner of the rectangular floor space which the machine occupies and two horizontal channel irons 11 extending across the top of the respective pairs of vertical channel irons l0 located at the corners of the longer sides of the rectangle. Each horioontal channel iron lll is securely connected to its respective pair of vertical channel irons l0 and suitable bracing members 12 `are provided in the angles between the vertical and horizon-tal channel irons. Other structural supporting members are used for carrying other parts of the machine as will presently be evident but the six members just described with their bracing members constitute the main Vsupporting structure.

The container is fabricated from sheet me-tal and has two vertical portions 13, 14 connected by a horizontal portion l5. One vertical portion l, which is about l2 feet high, extends from the region between the horizontal channel irons l1 at one end of the machine almost to floor level and its lower seven feet (apart from the last foot) forms the bed compartment 16 for a mass of particles. This compartment is nearly as wide as the distance between the two horizontal channel irons 11 (about six feet) but only about one foot in length. That part of the vertical portion l above the bed compartment is of the same width but about double the length being extended in rearward direction, that is to say towards the other vertical portion ifi, and this portion meets the horizontal portion l5 of the container just above the level of the horizontal channel iron-s lll. The horizontal portion l5 continues at this level towards the rear of the machine and there meets the other vertical port-ion 1d of the con- -tainer the top of which is conical in shape and leads to an exhaust conduit l?. r[he whole container is normally enclosed apart from transverse lslits 1S, i9 at the upper part of the rear and front faces which are provided to allow ingress and egress of the material to be dried. The vertical portion 113 and the horizontal portion 14 of the container thus define together an enclosed path of rectangular cross section through which the material to be dried may be led.

Adjacent the rear face of the container are mounted a pair of squeeze rollers Ztl, 21 journal blocks 22 for the ends of these being mounted directly on the horizontal channel irons lll. The lower roller 2l is normally journalled whilst the upper roller 2@ rests in vertically adjustable lmanner on the lower roller 2l. An adjustable counterweight 23 is provided so that the contact pressure of the upper roller 20 on the lower roller 2l may be varied.

Within the container are disposed transversely thereof a plurality of rollers which are to serve for the progressing and guiding of the material to be dried therethrough. Firstly there are .a series of tive rollers 24 disposed successively at the same level within the horizontal portion l5 of the container. These are followed at about two- `third-s the way along this portion of the container by a pair of cloth-guiding devices 25 of the known feeler type. lust over the rear edge of the eniarged upper par-t ifa of the vertical portion 13 of the container is journalled a special roller 26, the surface of which is scrolled opposite hand in the two halves in such a manner that when rota-ting in contact with a sheet of material a ,lateral tension will be induced in the latter. Within the enlarged par-t 15a is journalled in vertical adjustable man-ner a guide roller 27 provided with a weight support 23 which passes downwardly and out of the container so that weight may be applied thereto. At the same level as the scrolled roller 26 and somewhat forwardly thereof is journ-alled a guide roller 3h and at the same level as the weighted roller 27 but above the bed compartment is a further guide roller 31. Centrally disposed near the bottornof the bed compartment is journalled a hollow ceramic roller 32. At the top of the front vertical part 13 of the container and more forwardly still are journalled a pair of rollers 33, 34 their nip being substantially in line with the slit 19 at the front of the container. Somewhat below these rollers 33, 34 is journalled a rotatable rectangular rod 35.

The disposition of the rollers just described is clearly shown in Fig. 2 of the drawings whilst in Fig. l are shown only those rollers which are positively driven. Referring t-o Fig. l `a single motor 36 secured to the rea-r of the machine is used to drive the squeeze rollers 2t), 2l and the lfirst six rollers 24, 26 within the container. `The drive is transmitted via a belt or chain 37 and spur gears 3S, 39 to the squeeze rollers Ztl, 21 and then via a further heit or chain ill to the first tive rollers 24 wi-thin the container. Suitable belt or chain wheels il are provided which serve to guide and render adiustable the driving belt or chain 40. A still further belt or chain i2 drives the roller 26 through gear wheels 43, 4d. `A second motor tid mounted -on a suitable platform d6 at 'the front of the .machine `transmits a drive through .a chain or belt 47 to the rectangular rod 35. A third and final driving motor 4S drives the ceramic roller 32 in the bed compartment and the lower roller 33 of the final pair of rollers within the container through belt or chain drives 49, Sti as illustrated.

The remaining roller-s 27, Si), 3l, 34 within the container rotate only through their frictional contact with the material under treatment.

Further guide means for the material to be treated are provided at the Vrear and front of the machine. Thematerial itself, which can be up `to forty inches wide, maybe in the form of a roll l which is rotatably supported on a suit-able trestle 52 under the rear vertical portion 14 of the container. A `tie bar 53 between the two rear vertical channel irons 1f? serves to guide .the material on its way tothe squeeze rollers 2li, 2S.. The material may be taken off from `the machine by a driven roller, not shown, and a plain non-driven roller 54 may conveniently be mounted `across the front `upper `part of the machine to guide the cloth as it leaves the container.

The upper six feet of the lowertseven .feet of the front vertical portion 13 of the container, that is to say the bed compartment, is adapted to receive about two tons of finely divided silica sand. This sand is to be fiuidised and heated and for this purpose there must be provided, firstly, means for blowing air upwardly through the sand and, secondly, means for heating the sand. t

Accordingly, for fiuidising the sand, a source of compressed air is provided. This takes thefonn of a blower '55 which feeds, through suitable pipes Se and a gauge E57, airunder pressure to the lower foot `of the container beneath the bed compartment, which lower foot is separated from the bed compartment by a ceramic partition 58 by which the air is uniformly distributed to the bed of sand. The blowerd also feeds air under pressure to theceramic roller 32 in thebed of sand through a suitable pipe connection S9. This is to enabietha-t part ofthe bed of sand which would otherwise be shielded from the `main air flow by the material under treatment to be iiuidised.

For heatingthe bed of sand, gas heaters are provided. These take the form of hollow tubes oil which pass into the bed of sand from one side of the container and after performing two convo-lutions extending over the width of the bed compartment pass out of the container at the other side. There are convenientlyfourteen such pipes 6l?, seven entering from each side. At eachside of the container is disposed a gas supply manifold F61 whereby gas may be fed through normai jet arrangements d2 to each of the seven pipes dll. Also at each side is provided an exhaust manifold e3 through which the waste gases are extracted and passed away to the atmosphere by `twin conduits ed which lead to an extraction `fan'oS driven yby `a motorA 66 mounted on a platform 67 `at the front of the machine, finally passing away through a vertical staclr 63.

As the machine is of substantial overall height, about fourteen feet or more, it is desirable to provide a platform 69 around the upper part as illustrated in Fig. 5. The top of the horizontal portion l5 of the container is provided with removable covers, one shown open and one removed in Fig. 5, and the provision of the platform 69 facilitates inspection of the interior of the container after these covers 70 have been removed or opened.

In operation the bed compartment is filled with about two tons of silica `sand which has been previously Washed to remove fines, the overall diameters of the particles being within the range from to 200 microns. The end of the cloth 71 to be dried, which may have a moisture content of as much as 106% by weight is led between the squeeze rollers Ztl, 21 at the rear of the machine, through `the entrance slit 1S to the container, over the first ve drive rollers 2li, between the rollers of the cloth guiding devices 25', over the next driven roller 26, down into the enlarged portion of the front vertical portion 13 of the container, beneath the weighted roller 27, over the two foliowing guide rollers 36, 31 into the bed of sand in `substantially vertical disposition, under the ceramic roller 32, out of the bed of sand in substantially vertical disposition, between the nip of the two iinal rollers 313, 34 and out of the exit slit i9 of the container for collection. With the cloth so set up the fluidising and heating means are put into operation. The air feed is at a pressure of `about three pounds per square inch at the bottom of the bed, the volumetric flow being about forty cubic feet per minute at the operating temperature.

The velocity and nature of the current of air passing through the partition 5S and the roller 32 is such that the force exerted by the current is sufficient to counter- `balance the gravitational force on the free particles and to expand the bed thus allowing movement of the particles but is insufficient to convert the bed into a stream of particles. Gas is burnt at the `jets 62 at a rate of 56 cubic feet per minute and the hot gases pass into the tubes 6@ to maintain the temperature of the fluidised bed of sand at about C. This temperature is maintained by means lof a thermostat control which cuts off and brings on the gas supply as necessary.

The speed of the motors 36, 45, id driving the feed rollers 24, 26, 32, 33 for the cloth 71 is such that the cloth is progressed at a rate of 9) feet per minute through the container which gives a period within the container of about half a minute, with perhaps ten .seconds in the actual bed.

The rotating rectangular rod 35 which the cloth 71 normally passes over before emerging from the container serves to agitato the cloth as it leaves the iiuidised bed of sand andso dislodges any particles which may have adhered thereto, so that, they fall back into the bed.

if the bed of sand, when lluidised, is found to be too turbulent, this can be corrected by means of wire grids 72 or the like disposed substantially vertically at `each side of each run of the fabric and horizontally across the top of the bed.

On the machine just described various different types of textile fabrics have been successfully dried. These include, Torf/Iene, nylon, 106% viscoserayon and a mixture of 50% viscose rayon and 50% acetate rayon. rlibe detailslof temperature, drying times and so on given above were particularly suitable for the two latter fabrics.

it has been found convenient to utilize the large volume of steam which is liberated by the iiuidised bed of sand when in operation to eeot a prohosting of the cloth, which is approaching the bed of sand through the horizontal portion 15S of the container and the enlarged upper portion of the front vertical portion i3 of `the container. lu this region it `is also convenient to `stenter the cloth. The machine just described has proved successful for drying fabrics which arewet with water containing as much for instance as 103% by weivht of moisture.

Fabrics wet with dye liquor and a resin solution for example may also be successfully dried by the method according to the invention. The dye liquor or resin solution would usually be padded onto the fabric in the normal way and the fabric passed through a iiuidised bed to dry the fabric.

What we claim is:

l. A method of drying elongated flexible material wherein wet flexible material disposed in a substantially vertical plane is passed through a bed of hot solid discrete particles, while the bed is subjected to an upward gaseous current, the size and weight of the particles and the velocity and nature of the current being so chosen that the force exerted by the current is sucient to counterbalance the gravitational force on Vfree particles and to expand the bed thus ellowing movement of the particles but is insufcient to convert the bed into a stream of particles.

2. A method of drying according to the preceding claim in which the particles consist of silicious sand.

3. A method of drying according to claim 2 in which the particles are not less than 100 microns and not more than 200 microns overall diameter.

4. A method of drying according to claim 1 in which the gaseous current consists of air.

5. A method of drying according to claim 1 in which the gaseous current is applied through a porous ceramic partition.

6. A method of drying according to claim l in which the material is led into the bed in a downward substantially vertical direction and is led out of the bed in an upward substantially vertical direction, guide means being provided for changing the direction of the material in the bed.

7. A method of drying according to claim 6 in which the guide means includes a roller of porous ceramic material provided with an internal air supply to assist in maintaining a lluidised condition of the bed in the space between the ascending and descending portions of material.

8. A method of drying according to claim 1 in which the space occupied by the said bed is sub-divided by means of wire grids or the like sub-divisions for the purpose of reducing or eliminating turbulence.

9. A method of drying according to claim 1 in which the bed is heated by means of heat radiators located in the said bed.

10. A method of drying according to claim 1 in which the gas on leaving the bed is used to pre-heat the material.

l1. A method of drying according to claim 1 in which the material is stentered before entering the bed.

12. A method of drying water-wettened textile materials according to claim 1 in which the temperature of the said bed is not less than 100 C. and not more than 170 C.

13. A method of drying a wet elongated liexible material wherein the said material is led in a substantially vertical direction first downwardly and then upwardly through a hot fluidised bed of silicious sand, while the bed is subjected to an upward current of air the over` all particle diameter being not less than 100 microns and not more than 200 microns and the velocity of the air being sutlicient to counter-balance the gravitational force on free particles and to expand the bed but insucient to convert the bed into a stream of particles and the means for heating the said bed including heat radiators located in the said bed.

14. A method of drying according to claim 13 in which the wetting liquid consists of or contains a dye.

15. A method of drying according to claim 13 in which the wetting liquid consists of or contains a natural or synthetic resin.

16. An apparatus for the drying of elongated exible material, which includes a container adapted to contain a bed of solid discrete particles when in the uniluidised and when in the hot fluidised state, vthe overall particle diameter being preferably not less than microns and preferably not more than 200 microns, means for applying an upward gaseous current to the said bed at a pressure and velocity sufficient to counter-balance the gravitational force on free particles and to expand the said bed, thus allowing movement of the particles but insufficient to convert the bed into a stream of particles, means for heating the uidised bed and means for conveying material disposed in a substantially vertical plane continuously through the said lluidised bed.

17. An apparatus according to claim 16 in which the means for applying the said upward gaseous current includes a porous ceramic partition at or adjacent the bottom of the said container.

18. An apparatus according to claim 16 in which the means for heating the said iluidised bed include heat radiators disposed in the lower part of the said container.

19. An apparatus according to claim 16 in which the said means for conveying material includes rollers adapted to lead the material first downwardly and then upwardly in the interior of the said container.

20. A method of treating elongated llexible material wherein the material is passed through a bed of hot solid discrete particles, while the bed is subjected to an upward gaseous current, the size and weight of the particles and the velocity and nature of the current being so chosen that the force exerted by the current is sufficient to counter-balance the gravitational force on free particles and to expand the bed thus allowing movement of the particles but is insufficient to convert the bed into a stream of particles.

21. A method of treating elongated flexible material wherein the material disposed in a substantially vertical plane is passed through a bed of hot solid discrete particles, while the bed is subjected to an upward gaseous current, the size and weight of the particles and the velocity and nature of the current being so chosen that the force exerted by the current is suicient to counterbalance the gravitational force on free particles and to expand the bed thus allowing movement of the particles but is insuicient to convert the bed into a stream of particles.

22. An apparatus for treating elongated flexible material, which includes a container adapted to contain a bed of solid discrete particles when in the unuidised and when in the hot fluidised state, the overall particle diameter being preferably not less than 100 microns and preferably not more than 200 microns, means for applying an upward gaseous current to the said bed at a pressure and velocity suliicient to counter-balance the gravitational force on free particles and to expand the said bed, thus allowing movement of the particles but insufficient to convert the bed into a stream of particles, means for heating the uidised bed and means for conveying the material to be treated continuously through the said fluidised bed.

Minton July 27, 1915 Barnett Dec. 10, 1940 

